*{
    margin: 0;
    padding: 0;
}

html, body{
    width: 100%;
    height: 100%;
}

@keyframes dongHua1 {
    from{
        width: 400px;
    }

    to{
        width: 690px;

    }
}

.div1 img{
    width: 400px;
    height: 400px;
    background-size: cover;
    /* 需要应用动画的名字 */
    animation: dongHua1;
    animation-duration: 3s;
    animation-timing-function: ease-in;
    /* animation-delay: 1s; */
    animation-direction: alternate;
    animation-iteration-count: infinite;
}

@keyframes arrowDonghua {
    from{

    }

    to{
        bottom: 66px;
    }
}

.arrow{
    width: 44px;
    height: 44px;
    background: url(../img/arrow.png);

    position: fixed;
    left: 50%;
    bottom: 50px;

    animation: arrowDonghua 0.7s linear infinite alternate;
}
